1. Field of the Invention.
The present invention relates to inflation valves, such as are used in life raft inflation systems. In particular, the present invention is an improved bayonet for puncture disc inflation valves
2. Description of the Prior Art.
Inflatable life rafts have found wide use on ocean-going ships and aircraft. An inflatable life raft offers the advantage of light weight and small size. It is stored in its deflated condition for long periods of time when it is not needed, and yet can be inflated rapidly when it is needed to form a raft capable of holding people.
Inflatable life rafts are inflated using a pressurized inflation gas (such as carbon dioxide, dry air, or nitrogen) which is contained in a pressure tank or pressure vessel. When the raft is to be inflated, a valve is actuated by pulling a pull cable which is connected at one end to the valve actuating mechanism in such a manner as to allow the cable to pull free after the firing mechanism has been actuated. When the pull cable is pulled, the actuating mechanism fires the valve, causing it to open to permit the pressurized fluid to expand and fill the life raft.
One type of inflation valve which has been used in the past, is a "puncture disc" type of valve. This valve uses a disc (the "puncture disc") which normally blocks the passage connecting the inlet of the valve to the outlet of the valve. A bayonet or spear is provided for contacting and cutting or tearing the puncture disc open. An actuation mechanism is provided for moving the bayonet toward a sufficiently forceful collision with the disc to open the disc. Gas then flows from the pressure tank through the inlet, through the passage, and through the rupture in the puncture disc to the outlet and then to the inflatable article, such as a life raft.
Puncture discs of various kinds have been proposed in the past. Examples of puncture disc inflation valves are shown in the following U.S. patents. Hinchman U.S. Pat. No. 2,120,248; Davis U.S. Pat. No. 3,266,668; Bernhardt et al U.S. Pat. No. 3,526,339; Martin U.S. Pat. No. 3,757,371; McDaniel et al U.S. Pat. No. 3,887,108; Milgram U.S. Pat. No. 3,938,704; Legris U.S. Pat. No. 4,356,936; and Mackal U.S. Pat. No. 4,475,664.
Prior art bayonets have been subject to occasional misfire, probably as a result of tearing or incompletely cutting the puncture disc. Such misfires include the bayonet penetrating the puncture disc, catching on the disc and failing to clear the disc thereafter to allow gas to pass therethrough. Tearing or shearing of the disc can also result in portions of the disc breaking free and jamming elsewhere in the valve. Shearing of the metal of the disk also requires more force than cutting through the disc. Such misfires result in slow or incomplete inflation of the life raft. Such misfires occur most commonly under marginal operating conditions which may be the result of extreme weather where rapid and complete inflation of the raft may be most urgently needed.